The present invention relates to metering products, in particular liquid product, and to filling containers with the metered products.
In many production fields, e.g. the chemical-pharmaceutical industry, food, cosmetic and other industries, containers, e.g. bottles, must be filled with a metered quantity of products, in particular a liquid product.
According to regulations in force in different countries, a predetermined minimum nominal net weight, as well as a predetermined difference margin, should be indicated on the package.
Many solutions have been heretofore used in different machines for metering liquid product and for filling the containers.
According to one of the known methods, a constant volume of liquid product, obviously corresponding to the required nominal net weight, is determined considering the product density.
The metered quantity of product is introduced into the containers by suitable delivering means, e.g. nozzles.
The container is weighed before the filling and after the filling, in order to control if the metered volume is constant and to define tare and gross weights.
The values obtained by the above mentioned weighing operations are processed by a suitable electronic unit, which calculates the effective net weight of the liquid product introduced into the container.
If the obtained effective weight of product is lower than the minimum acceptable weight, suitable additional delivering means introduce another portion of liquid product, constant or proportional to the error entity.
However, according to this solution, the final weight of the liquid product introduced into the container is not measured again, therefore, the volume of the introduced product is not guaranteed.
One of the disadvantages of the known machines derives from the inevitable wearing out of liquid delivering means and the feeding means joined thereto.
This results in the need of further volume correction, e.g. by introduction of another quantity of liquid through the above mentioned additional delivering means.
Analogous problems of volume variation are connected with possible temperature variations, particularly if the product density is considerably influenced by the temperature.
According to another known method, the containers are filled until a predetermined level by delivering means provided with suction means working in the area of the filling level.
However, this solution does not guarantee a constant volume in case of containers having different cross sections.
According to still another method, the liquid product is delivered in two subsequent steps.
During the first step, the containers are filled with a relatively high speed, but not completely, while during the second step, the containers are filled slowly until the predetermined net weight is obtained.
The apparatuses carrying out the above mentioned method are usually rather complicated and their working time is long.
These apparatuses usually include a plurality of working groups, which weigh, in time relation, the containers, so as to determine the tare weight, and deliver liquid products.
The Belgian Patent No. 901.407 claims a method for filling containers, which includes measuring the tare weight of the single container, in a first weighing station; transferring of this container to an initial filling station, where the product is delivered until 90% of nominal net weight is obtained; measuring of the gross weight of the partially filled container in a second weighing station; transferring of the partially filled container into a final filling station, where the filling is completed by delivering an additional quantity of product, which is determined by processing means, supplied with data obtained by the above mentioned measuring operations.
However, this method does not include controlling of the additional quantity of delivered product, therefore, it is not possible to correct possible variations deriving from e.g. problems of the delivering pump.
According to yet another method, a liquid product is delivered to the containers for a predetermined period of time, at a constant flow rate, so as to deliver a quantity of liquid products proportional to the delivery time.
The above mentioned method is carried out by machines, which include a liquid feeding reservoir, inside which there is pressure realized by a suitable gas.
A feeding channel, extending from the reservoir, has a delivery nozzle at its end and is equipped with a valve means, which is activated by timer means.
The drawbacks of this solution derive from the lack of precision resulting from a gradual reduction of level in the feeding reservoir and from a consequent variation of the delivery pressure, which influences the flow rate.
This disadvantage is sometimes outweighed by gradual increase of liquid delivery time, however, it does not guarantee the introduced quantity, since the weight of the product really introduced into the containers is not determined.
There are also other methods, different from the just described, or combining some of their characteristics.
The Italian Patent application No. 3546A/87 claims a method for batching products by subsequent corrective deliveries in relation to weight checks, which includes the transferring of the containers through subsequent delivering stations, alternate with weighing stations. In each delivering station an additional quantity of product is delivered in relation to the weight check carried out in the previous weighing station. In the final delivering station, a further correction is carried out, some quantity of product is added or taken away, depending if the final obtained weight is smaller or bigger than the nominal one.
The U.S. Pat. No. 5,156,193 claims a method for filling containers, which includes: measuring of the container tare weight in a first weighing station; filling of this container with liquid product in a delivering station; measuring of the full container weight in a second weighing station; processing of the data coming from the above mentioned weighing stations, as well as of the data concerning the pressure and temperature of the delivered products, in order to determine the delivery time necessary for filling the subsequent container up to nominal net weight within an acceptable variation.
The German Patent No. DE 2660164 discloses a method for metering liquid product, which uses a metering container submerged in the liquid to be delivered to the containers, inside a suitable reservoir.
The metering container moves vertically, so as to engage, during its upward stroke, a perforated plug, which communicates axially with a nozzle connected to a liquid product discharge pipe.
The inner volume of the metering container defines the metered quantity sent to the container, as a consequence of the relative movement between the metering container and the plug acting as a piston.
However, this solution features considerable drawbacks resulting from tightness and wear of the parts which are in contact with liquid product, in particular the nozzle.
Consequently, different methods used so far for filling containers with liquid product and the like, usually require complicated machines, because of the presence of a series of weighing stations and a series of delivering means, which results in higher maintenance costs, in particular for cleaning and substitution of worn parts.
Moreover, these machines usually do not guarantee the metering precision.
Another disadvantage of the above mentioned machines is encountered during change over operation, which requires change of the metered quantity of products. The change over usually requires complicated operations for replacement of the parts involved in the filling process.
According to a device known in the art, shown in FIGS. 1 to 4, a reservoir 3 is fed with the liquid product 10 to be introduced into containers 2. The reservoir 3 is periodically supplied by a suitable supply duct 4, so as to maintain constantly the product level within the range defined by sensor means 5 and 6.
A metering receptacle 7, open at the top, is situated inside the reservoir 3. A movable element 13 moves first to a filling position, in which it is lowered into the liquid product 10 contained in the reservoir 3, so as to raise the level of the product 10 over the opening 7a of the metering receptacle 7.
Then the element 13 moves to a raised non-filling position, in which the level of the liquid product goes down below the above mentioned opening 7a and a metered quantity 11 of liquid product is collected inside the metering receptacle 7.
Lastly, the metered quantity of liquid product 10 is delivered to the container 2, which is dwelling under the metering receptacle 7, by connecting the container with the relative discharge pipe 8, which is for instance extendible (FIG. 4).
The prior art method includes a periodical feeding of liquid product 10 to the reservoir 3, so as to maintain the level of the liquid product 10 within a pre-determined range defined by the level sensors 5, 6.
In accordance with this known method, document BE-523,137 discloses a device for filling a plurality of containers, in which metering vessels are placed inside a basin filled with liquid product up to a level lower than the rims of the vessels. A plunger is dipped into the liquid product to raise the level over the rims of the vessels, which are filled. Then the plunger is raised up again and the liquid contained in the is delivered to the containers dwelling under the metering vessels.
Document FR-2,182,616 describes a machine for filling containers, in which a series of metering vessels are periodically filled with liquid product until the product overflows therefrom. The liquid overflown is collected into containers placed at both sides of the machine and connected to each other by a plane through which the metering vessels pass. The liquid contained in the vessels is delivered to the containers to be filled.
A series of plunger are inserted in the metering vessels to adjust the capacity thereof in accordance with the size of the container to fill.
Also document U.S. Pat. No. 5,224,526 uses a series of plungers to change the capacity of metering chambers by inserting the plungers more or less into the chambers. The chambers are then periodically filled with liquid product from a tank which is at a lever over the rim of the metering chambers, so that the liquid product overflows therefrom and is collected by collecting tubes surrounding the metering chambers and leading to a collecting reservoir.
The prior art methods fulfill the object of filling the containers with a metered quantity of liquid product, ensuring the exact correspondence of the this metered quantity to the predetermined nominal value.
In fact, the definition of the metered quantity is given by the volume of the metering receptacle or vessels. Basically, the quantity of liquid product delivered to each container is exactly the volume of the metering receptacle or vessel. Slight variations are obtained by inserting more or less a plunger in the metering receptacle or vessel.
It should be noted that keeping the level within a defined range, which is necessary in those machine which use a plunger to raise the level of the liquid to fill the metering receptacles, brings about some disadvantages.
First, the need of two level sensors, one for the maximum level and one for the minimum level. This means a more complicated control of the device operation.
Second, the amount of liquid flowing into the metering receptacles or vessels depends on the volume of the plunger, and also the amount of liquid to be delivered is limited by the dimension of the whole container. The dimension of the machine shall be increased to allow filling containers of a wide size range.
Moreover, none of the prior art methods discloses the use of the plunger to periodically define the volume of the liquid inside the metering receptacle or vessel, each time the receptacle or vessel is filled. This means that the plunger is not an active member of the device, while acting inside the metering receptacle or vessel, but rather a passive adjustment means.
Due to this fact, the dimension of the machine cannot be reduced by exploiting the space inside the metering receptacle or vessel in combination with an active use of the plunger.
The object of the invention is that of providing a method for filling containers with metered quantities of liquid product, which ensures a precise quantity of product introduced in the containers, an easy change over for different containers, by which also the metered quantity of liquid product is changed, and which requires a simple manufactured machine, practical, versatile and whose operation speed is high.
Another object of the invention is to provide a method and machine in which the quantity of the liquid delivered to the metering receptacle does not depend on the dimension of the plunger of the prior art, and the dimension of the whole reservoir is not critical to the quantity of liquid to be supplied to the containers being filled.
Another object is to provide a method and a machine which use the plunger of the prior art as an active element to define the quantity of liquid product inside the metering receptacle.
The above mentioned objects have been obtained, in accordance with the contents of the claims, by means of a method for metering products, in particular liquid product, and for filling containers with metered products, said method including:
feeding products to a reservoir, which is in communication with a metering receptacl, said metering receptacle having an upper part with an opening and a lower part equipped with a discharge pipe directed to a container to be filled, and with valve means situated along said discharge pipe;
operating level changing means for filling said metering receptacle, said level changing means increasing the level of products contained in said reservoir, so as to cause the filling of said metering receptacle with said articles and the definition of a metered quantity of said products inside said metering receptacle;
delivery of said metered quantity of products to said container through said discharge pipe, by opening said valve means;
the method being characterized in that, operation of said means for feeding said metering receptacle includes:
bringing a moving element inside said reservoir;
feeding said products to said reservoir until said products reaches a predetermined level over said opening of said metering receptacle, so as to fill up said metering receptacle;
removing said moving element from said reservoir, so as to lower the level of the products therein below said opening of said metering receptacle.
According to another embodiment of the invention, after having fed the metering receptacle with a quantity of products exceeding the quantity necessary for filling up the receptacle, the method includes:
completing the filling of said metering receptacle with said products, so as to define a metered quantity of said products inside said metering receptacle;
introduction of a moving element into said metering receptacle, so as to make the quantity of products exceeding the quantity necessary to define said metered quantity overflow through said opening of the metering receptacle;
delivering said metered quantity of products to the container through said discharge pipe, by opening said valve means;
transferring the quantity exceeding the metered quantity to a second metering receptacle, said second metering receptacle being set in communication with a second container to be filled, with working cycles of said metering receptacles being alternatively operated in the introduction and delivery steps.
According to another embodiment of the method, after that a moving element has been introduced into the metering receptacle, so as to make the quantity of products exceeding the quantity necessary to define said metered quantity overflow through said opening of the metering receptacle, the quantity exceeding the metered quantity is collected into a collection tank, from which it is reintroduced into the close product introduction circuit.
The method described heretofore is carried out by a machine for metering products, in particular liquid product and for filling containers with metered product, characterized in that it includes:
a reservoir, with a bottom, for feeding products;
a metering receptacle, which is set in communication with said reservoir and with the container to be filled, said metering receptacle having an upper part with an opening and a lower part equipped with a discharge pipe directed to a container to be filled, with valve means situated along said discharge pipe;
a first element, moving between a lowered, filling position, in which it is introduced into the products contained in the reservoir, and a raised, non-filling position, in which it is removed from the products;
the machine being characterized in that it further includes:
a supply duct for cyclically introduce liquid product into said reservoir until a predetermined minimum level, over the opening of said metering receptacle, is reached and in phase relation with the filling lowered position of said first moving element;
sensor means, which detects said minimum level of liquid product in the reservoir and sends a signal for closing said supply duct.
According to a different embodiment of the invention, the machine includes:
a metering receptacle situated inside the reservoir and connected with the container to be filled;
a supply duct which cyclically feeds the metering receptacle with a quantity of liquid product exceeding a metered quantity to be obtained;
a moving element, which is introduced into said metering receptacle, so as to reduce the nominal volume thereof up to a value equal to the metered quantity, due to overflowing of the quantity of products exceeding the metered quantity;
means for collecting the exceeding quantity of products expelled from the metering receptacle;
means for emptying the reservoir from the products, which have overflown therein during the filling of said metering receptacle;
the machine being characterized in that said means for collecting said exceeding quantity of products include a second metering receptacle, which is arranged with respect to the first metering receptacle in such a way that the respective upper openings are aligned and connected to a plate, said second metering receptacle being connected to a relative second moving element and equipped with a respective nozzle, which is a branch of said supply duct, said second metering receptacle being connected to a corresponding second container to be filled and in that it includes interconnecting means for connecting said moving element and second moving element in a determined phase relation, so that when one moving element is introduced into the relative metering receptacle, the other is removed therefrom and vice-versa.
According to a different embodiment of the claimed machine, the machine includes a plurality of metering receptacles arranged in a ring inside the collection tank, said collection tank having a circular base and being set into rotation in synchrony with carrousel means, which move the containers to be filled, so as to place them below the corresponding metering receptacles, said metering receptacles being connected with relative volume reducers, which are driven to move vertically by respective guiding means engaged by a track of a ring-like cam, which is coaxial with the carrousel and fastened thereto.